Bag filter arrangement

ABSTRACT

A bag filter apparatus that removes entrained particulate matter from a carrier gas stream is disclosed. The bag filter has a novel flow arrangement that provides for a sudden expansion of the carrier gas to thereby lower its velocity and thus reduce its capacity to carry particulate matter while it precludes direct impingement of entrained particulate matter upon the fabric filter bags to reduce abrasion of the fabric. The flow arrangement defined also increases the collecting efficiency of the filter bag by eliminating the re-entrainment of filtered dust in the gas stream after it has been once removed therefrom.

United States Patent 1 Anderson et al.

[ June 19, 1973 BAG FILTER ARRANGEMENT [75] Inventors: William M.Anderson; Ronald J.

Renko, both of Wellsville, NY.

[73] Assignee: The Air Preheater Company, Inc., Wellsville, NY.

[22] Filed: Dec. 20, 1971 [21] Appl. No.: 209,806

[52] US. Cl 55/302, 55/319, 55/341 [51] Int. Cl 801d 46/04 [58] Field ofSearch ..55/301305, 319, 341, 361-382, 418, 424

[56] References Cited ,UNITED STATES PATENTS 1,743,934 1/1930 Ruemelin55/341 X 3,385,033 5/1968 Basore et al.... 55/341 X 3,499,268 3/1970Pausch 55/341 X 3,513,638 5/1970 Young 55/341 X Sharlit 55/304 Nepereny55/341 -X [57] ABSTRACT A bag filter apparatus that removes entrainedparticulate matter from a carrier gas stream is disclosed. The bagfilter has a novel flow arrangement that provides for a sudden expansionof the carrier gas to thereby lower its velocity and thus reduce itscapacity to carry particulate matter while it precludes directimpingement of entrained particulate matter upon the fabric filter bagsto reduce abrasion of the fabric. The flow arrangement defined alsoincreases the collecting efficiency of the filter bag by eliminating thereentrainment of filtered dust in the gas stream after it has been onceremoved therefrom.

5 Claims, 1 Drawing Figure BAG FILTER ARRANGEMENT BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to porousfiltering devices for removing particulate matter from a dirty gasstream in which the filtering device comprises a tubular filter bagdirectly exposed to a stream of dirty gas while a cleaning means isprovided for removing accumulated dust deposits from the filteringsurfaces of the filter. Usually the bag cleaning means comprisesapparatus that sets I up a momentary back pressure to cause reversefluid flow within the filter bags and thus to remove accumulated dustfrom the outer surface thereof. As the back pressure subsides, the dustparticles dislodged from the filter bags frequently are re-entrained inthe oppositely flowing dirty gas stream to be again subjected to thefiltering action and deposited on the surface of the filter. The filterelements thus are forced to repeatedly remove the same particles fromthe gas stream whereby such elements become inefficient and worn withuse and cleaning becomes a slow operation.

SUMMARY OF THE INVENTION The present invention comprises a bag filterarrangement through which dust entrained gases are directed to removethe dust particles from the gas. The bag filtering units are arranged inlongitudinal banks laterally adjacent a horizontal inlet duct carrying astream of dust entrained gas. The gas is exhausted upward from anelongate opening in the inlet duct and is turned downward by theunderside of a horizontal tube sheet. Quantities of agglomerated dustcake being removed from the filtering units fall downward in the samedirection as the circulating inlet gas stream so that said dust is notre-entrained in the incoming gas and again deposited on the surface ofthe filter. The inlet duct for dust entrained gas is moreover designedto provide a sudden increase in volume whereby the gas with dustentrained therein expands rapidly after exhausting from an elongatedslot, whereupon it loses velocity to drop a portion of the heavierparticles entrained therein into a subjacent collection hopper. Aperforate service walkway is provided above the elongate opening in theinlet duct to utilize available space for service and repair, and toprovide an even pressure distribution throughout the housing byproducing a slight pressure drop thereto.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE is a perspectiveelevation, partially broken away to show a filter arrangement accordingto the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention ahousing is formed with a rectangular main filter section 10 and a hoppersection 12 subjacent thereto. The main housing 10 includes a transversetube sheet 14 dividing the housing into a filter chamber and a clean gasoutlet chamber. The tube sheet has a series of apertures 16 with alignedcollars 18, each of which provides a clamping base for a perforatefilter bag 22. An inlet port 15 for dust entrained gas enters laterallyinto the hopper and an outlet 26 for clean gas is connected to the upperpart of the housing to exhaust clean. gas therefrom.

In order that reversely flowing air is provided to remove the filtereddust particles from the outer surface of each filter bag, a cleaningnozzle 32 connected to a source of compressed air (not illustrated) isdirected axially into the upper open end of each filter bag 22. As thepressure within each bag increases, the bag flexes outwardly whereuponthe-dust deposits are detached from the outer surface of the filter bagand permitted to gravitate to the hopper 12. Collections of dustdeposits are eventually removed through a removal gate 34 at the bottomof the hopper.

In accordance with this invention, an elongate inlet duct 36 extendstransversely along the length of the hopper 12 from the inlet port 15 tothe opposite wall. The inlet duct 36 is provided along its top side withan elongate outlet opening or slot 38 through which dust entrained gasis directed upward into the central portion of the filter chamberbetween banks of filter tubes where it may expand suddenly and lose muchof its ve locity. As the carrier gas loses velocity, it also loses theability to entrain and carry particulate matter. Thus much of theparticulate matter drops out of the carrier gas stream and falls to thebottom of the inlet duct 36 where a narrow slot 42 permits theparticulate matter to fall therethrough to the hopper 12.

'The slot 42 is much more restricted than the elongate top opening 38whereby the gas stream in the inlet duct 36 will follow the path ofleast resistance and as a result flow freely upward to expandinto thefilter chamber, lose velocity and drop the heavier particulate mattercarried thereby to the bottom of the duct 36.

The elongate top opening 38 is at the center of the inlet duct in themain housing section 10 intermediate banks of collecting filter bags 22.Thus, gas exhausting from the slot 38 rises through the central voidbetween banks of filter bags and is turned laterally by the underside ofthe tube sheet 14. After the gas is turned laterally it circulatesdownward along the filter bags and eventually traverses the intersticesbetween fibers thereof and deposits the fine particulate matter carriedthereby on the surface of the filter bag. Thus, only gas free fromentrained dust particles traverses the fabric filter and flows to theupper end of the filter bags and out through collar 18 to the clean gasoutlet chamber and outlet duct 26.

As particulate matter collects on the outer surface of the filter bag itreduces the flow of dust entrained gas therethrough and must beperiodically removed to permit the flow of said gas to continue. Theparticles collecting on the upstream surface of each bag are removedwhen a blast of compressed air from a predetermined source (notillustrated) is directed through the supply ducts 30 to the cleaningnozzle 32 and into the open end of each bag filter. The blast ofcompressed cleaning air momentarily reverses the flow through thefilter, flexes the bag outwardly and breaks the collected dust cake fromthe outer surface thereof. As the dust cake falls down it is carriedalong to the collection hopher. However, it would be considered withinthe purview of this invention to provide a grating having graduatedapertures designed to provide an even more constant distribution offluid throughout the housing.

Thus while only a single form of the device has been disclosed in thedrawing, it will be understood that various concepts defined herein maybe applicable to other sizes and shapes of apparatus employed for thestated purpose. It is therefore to be understood that various changesmay be made in the details of construction without departing from thespirit of the invention.

We claim:

1. Apparatus for separating particulate matter from a carrier gascompromising a housing, a dust hopper subjacent said housing andattached thereto, an inlet for dust entrained gas at one end of saidhopper, an outlet for clean gas adjacent the upper side of said housing,an apertured tube sheet extending across said housing intermediate theinlet and outlet openings to separate the housing into filter and outletchambers, duct means extending from the inlet end to the opposite end ofsaid hopper to direct dust entrained gas therethrough, filter bagsdepending from said tube sheet at the sides of said duct means toprovide an expansion chamber having a void, an elongate opening in thetop of said duct means subjacent said void and adapted to exhaust thedust entrained gas vertically, and cleaning means adapted to removecollected dust particles from the outer surface of said filter bags anddrop them to the subjacent collection hopper for removal from saidapparatus said duct means having an opening at the bottom thereof topermit heavy particulate matter carried by said gas to fall directlyinto said hopper.

2. Apparatus for separating particulate matter from a gas as defined inclaim 1 wherein the duct means extending from inlet to the opposite endof the hopper is cylindrical to preclude the accumulation of particulatematter in said duct means.

3. Apparatus for separating particulate matter from gas as defined inclaim 2 wherein the opening at the bottom of the duct means comprises anelongate slot that permits the movement of particulate mattertherethrough.

4. Apparatus for separating particulate matter from gas as defined inclaim 3 wherein the opening along the top of the inlet duct has agreater area than the elongate slot at the bottom of said duct.

5. Apparatus for separating particulate matter from gas as defined inclaim 1 including a perforate grating extending along the opening at thetop of said duct means to provide a catwalk giving access to the filterbags of said apparatus and simultaneously restrict flow to establish apressure differential between the inlet duct and the filter chamber.

1. Apparatus for separating particulate matter from a carrier gascompromising a housing, a dust hopper subjacent said housing andattached thereto, an inlet for dust entrained gas at one end of saidhopper, an outlet for clean gas adjacent the upper side of said housing,an apertured tube sheet extending across said housing intermediate theinlet and outlet openings to separate the housing into filter and outletchambers, duct means extending from the inlet end to the opposite end ofsaid hopper to direct dust entrained gas therethrough, filter bagsdepending from said tube sheet at the sides of said duct means toprovide an expansion chamber having a void, an elongate opening in thetop of said duct means subjacent said void and adapted to exhaust thedust entrained gas vertically, and cleaning means adapted to removecollected dust particles from the outer surface of said filter bags anddrop them to the subjacent collection hopper for removal from saidapparatus said duct means having an opening at the bottom thereof topermit heavy particulate matter carried by said gas to fall directlyinto said hopper.
 2. Apparatus for separating particulate matter from agas as defined in claim 1 wherein the duct means extending from inlet tothe opposite end of the hopper is cylindrical to preclude theaccumulation of particulate matter in said duct means.
 3. Apparatus forseparating particulate matter from gas as defined in claim 2 wherein theopening at the bottom of the duct means comprises an elongate slot thatpermits the movement of particulate matter therethrough.
 4. Apparatusfor separating particulate matter from gas as defined in claim 3 whereinthe opening along the top of the inlet duct has a greater area than theelongate slot at the bottom of said duct.
 5. Apparatus for separatingparticulate matter from gas as defined in claim 1 including a perforategrating extending along the opening at the top of said duct means toprovide a catwalk giving access to the filter bags of said apparatus andsimultaneously restrict flow to establish a pressure differentialbetween the inlet duct and the filter chamber.